The trichothecenes are a large group of fungal toxins that are commonly encountered as food contaminants and that have been etiologically linked to human gastroenteritis worldwide. These compounds and related agents such as ricin and shiga toxin which interfere with ribosome function are of further concern for their potential use in chemical terrorism and warfare. Ribosome-directed agents are believed to act via a mechanism involving mitogen-activated protein kinases (MAPKs) and termed the "ribotoxic stress response". However, a critical knowledge gap exists relative to signal transduction mechanisms by which ribotoxins activate MAPKs and subsequently initiate inflammatory gene expression and apoptosis. The long term goals of this research are to characterize the molecular mechanisms by which ribotoxic agents cause intestinal disease and to devise strategies for prevention or treatment. The objective of this proposal is to identify the intracellular signaling pathways and receptor mechanisms by which the model trichothecene deoxynivalenol (DON or "vomitoxin") induces p38 MAPK activation and relate these to inflammation and apoptosis. Our central hypothesis is that double stranded RNA-activated protein kinase (PKR) and hematopoietic cell kinase (Hck) are critical for trichothecene-induced p38 activation and downstream toxicity. To test this hypothesis, our research team will use 1) knockout mice to verify roles for PKR and Hck in p38 activation and downstream toxicity and 2) macrophages to elucidate signal transduction elements that link DON to p38 via PKR and Hck. Four specific aims are proposed: 1) Characterize the role of PKR in DON-induced p38 activation and downstream toxic effects; 2) Characterize the role of Hck in DON-induced p38 activation and downstream toxic effects; 3) Assess role of the ribosome to DON-induced p38 activation; and 4) Evaluate role of alternative receptors in DON-induced p38 activation. Several outcomes are anticipated to arise from this work. First, we expect to have an improved understanding of the molecular basis by which trichothecenes and other ribotoxic stressors disrupt gut mucosal immune function by deregulating macrophage function. Second, these data will directly inform human risk assessment efforts by identifying specific hazards associated with acute and chronic exposure to trichothecenes and other ribotoxic agents as well as provide a basis for rational risk management. Third, this research will yield mechanism-based strategies for preventing and/or treating toxic effects in persons exposed to trichothecenes and ribotoxic chemicals in foods via natural contamination or as a result of deliberate use in chemical terrorism or warfare. Collectively, these outcomes will positively impact human health by providing a scientific basis for generating sound public health recommendations relative to this important class of toxins and appropriate remedial actions should exposure occur.